This invention relates to a cartridge for recording medium, and more specifically to a shutter for opening and closing the head access slot of a cartridge for recording medium.
A conventional disk cartridge for recording medium will be described below in conjunction with FIG. 1 illustrating an embodiment of the present invention. Generally, a disk cartridge 10 is equipped with a shutter 50 that opens and closes openings 31 formed in the upper and lower shells of the cartridge case, the openings combinedly forming a slot for the access of a magnetic head. When the cartridge is not in use, the shutter 50 is urged by a spring in one direction to close the head slot 31 (FIG. 1(a)) and, when the cartridge is used, the shutter is moved in the opposite direction by a mechanism of a drive unit to an open position (FIG. 1(b)). The shutters of this character in extensive use thus depend merely on spring action for their closure and can be easily opened by children. The tampering can damage the recording media housed in the cartridges. Because of this concern and also because of the potential application to the cartridges for game software, an early improvement in the closing mechanism has been awaited.
Provision of some locking member to keep the shutter immovable when not in use has already been proposed.
However, the prior art cartridges equipped with such locking members have one disadvantage or another. For example, the cartridge must be thick enough to form a groove or notch that is required to receive an unlocking member (Japanese Utility Model Application Kokai No. 56377/1983). An unlocking part for the locking member provided in the space between the upper and lower case shells or inside the shutter complicates the construction of the unlocking member and the shutter opening-closing member on the part of the recording-reproducing unit (Japanese Patent Application Kokai No. 56377/1994).
The prior art structures will now be considered in detail. FIG. 4 shows a shutter locking mechanism for a disk cartridge described in Utility Model Application Kokai No. 56377/1983. A slide shutter 120 is disposed between upper and lower shells 111 (only one of which is shown) of a cartridge case containing a magnetic disk. The shutter is biased by a spring in the direction of an arrow A. In one piece with the inner wall at a corner of the case made up of the upper and lower shells, there is formed a locking member 133 having a locking pawl 137 at the front end, generally in the form of a cantilever plate spring. The locking member 133 is formed substantially in parallel with one edge of the case. The space above the locking member 133 constitutes a guide groove 125 defined by the upper and lower shells, along which an unlocking pin 128 of a recording-reproducing unit is to slide.
Normally the shutter 120 is shifted in the direction of an arrow A where its locking hole 139 is engaged with the locking pawl 137. As the disk cartridge is loaded into the recording-reproducing unit, the unlocking pin 128 enters the guide groove 124 from the direction of an arrow B, depresses a protuberance 138 of the locking member 133, thereby releasing the pawl 137 from the locking hole 139 of the shutter 120, and finally opens up the shutter 120.
The locking mechanism is disadvantageous in that the guide groove 125 required to guide the unlocking pin renders it impossible to reduce the overall thickness of the case of the disk cartridge. Another disadvantage is the questionable reliability of locking, since the locking member, a cantilever type having the locking pawl 137 distant from the supported base and molded of plastic material, becomes unable to maintain precise locking pawl engagement after repeated use.
Patent Application Kokai No. 60592/1994 teaches a shutter locking spring 206 as shown in FIG. 5. A slide shutter 202 is mounted astride on one edge portion of a disk cartridge 201 and is normally biased leftwards as viewed in the figure by a spring 205. The shutter locking spring 206 is a cantilever spring fixed at the base to the cartridge case. It has a locking dent 207 near its free end, which is adapted to receive a locking protuberance 203 formed on the shutter, so as to lock the shutter in the closing position. The case is formed with a groove 214 to receive an unlocking pin 210.
This locking mechanism again requires the groove 214 to guide the unlocking pin, which hampers an effort to reduce the overall thickness of the disk cartridge case. Similarly, the other disadvantage is the inability of ensuring positive locking. The cantilever type locking member, the long distance from its base to the locking dent 207, and the plastic molding combine to make it gradually difficult, after repeated use, to maintain exact locking pawl engagement.
In view of these, there has been a demand for a cartridge that eliminates these disadvantages of the prior art and provides perfect protection for the recording medium contained.
The present invention therefore has for its object to provide a cartridge whose shutter can be positively locked when closed to provide perfect protection for the recording medium, and which is reduced in overall thickness and simplifies the unlocking mechanism and shutter-opening-closing mechanism of the recording-reproducing unit with which the cartridge is used.